Program phase reverses



Patented' Ma -'16, 193a.

PROGRALI PHASE REVERSED Jarrett L. Hathaway, Manhasset, N. Y aasignor to Radio Corporation of America, a corporation of Delaware Application October 7, v1937, Serial No. 107,109

10 Claims.

This invention relates to systems for controllingthe signals derived from a microphone in such manner that the peaks of sound waves which may at times be greater in one direction 5 than in the other are impressed upon the usual amplifiers with suitable phase for obtaining an optimum condition of linear amplification. With system or unsymmetrical limitation, this permits greater undistorted output power. v

In broadcasting, sound recording, and in various sound pickup systems, including public address systems, it has been found that the elec trical circuits involved have greater latitude in one phase than in the reverse, that is, linearity tion than in the reverse. Therefore, for maximum undistorted speech or program power to be transmitted through such a system, it is essential that the phasing of the voice frequency wave be 2a made such as to place the maximum pealcs in the direction of greatest latitude. The'hurnan voice often has as much as a turo-to-one diiterence in the peak amplitudes on the positive and neon-- tive sides of the sound wave. In normal program worlr microphones of I the so-called "velocity" type are often used, and these microphones are are so disposed with respect to the performers that they pick up sound Waves from either one or both sides. Maximum peaks oi electromotlve 30 force excited by a human voice are of one phase ior one side of the microphone and the opposite tor the reverse side. In a radio broadcast program it is frequently necessary also to shift the circuits or lines from one microphone to another or to change the location oi diflferent microphones. as a result frequent phase reversals occur.

it is an object of my invention to provide a program phase reversing device which willenso able a microphone to be utilized in such manner that any amplifier or speech circuit in which non-linearity in one direction is reached at lower amplitude than in the reverse, will have applied thereto a speech wave whose unsymmetric wave 45 peaks are suitably phased for placing these peaks often extends over a greater range in one direc- I detail, reierence being made to the accompanying drawing, in which the sole figure thereof represents a circuit diagram of a preferred embodiment'.

- Referring to the drawing, I show an audiowave phase reversing arrangement in which there is provided an input transformer 5 having two secondary windings of suitable impedance 6 and "l. The secondary winding 6 feeds audio signals to a primary winding of suitable impedanceoi an output transformer 32. This primary windthe has two portions 33 and 34, the respective circuits and connections of which are completed through the back and ,front contacts of relayoperated switch, presently to he described. Be-

tween these contacts there is a movable contact sprlna c connected withi one terminal of the secsecondary winding 6, either to the upper portion it or the lower portion t l at the primary on transiormer ti, thus reversing the phase of the output.

The secondary winding "l oi transformer t is shunted try a potentiometer it having an adjustable top which feeds to the control grid of an amplifier tube ii. The grid of tube 9 has a direct current bias from source it through an adjustable tap W on the potentiometer it. The output circuit from this tube includes the-primary winding of a transformer it which also has two secondary Windlass it and It. In shunt with the primary oi transformer i0 is a potentiometer it, from which energy may be tapped at a selected voltage for controlling detector tube It. This energy is directed through a blocking condenser ii, to the'grid of said tube N, which tube is preferably oi the grid leak detector type. operating with zero bias at no signal, It being the grid leak resistor. The output circuit of the tube M includes a relay II, which is fed with direct current from the source 2|. In the absence of signo]: the tube i4 is conductive and, therefore, permits the relay 2! to be energized. In the presence 01 signals, however, the grid 01' the tube 14 is negatively biased to a point where the tube impedance causes the relay II to release.

V J. L. HATHAWAY 2,158,826

PROGRAM PHASE REVERSER" Filed Oct. 7, 19:57

' "ilk/100"? AMBER GREEN a?) gym/1117mm f BY lfldN/ MM l/ mman The amber glass being more translucent at low filament temperature of the lamp than the green gives the impression that lamp 3' only is lighted when current passes through both lamps in series; whereas, when the amber lamp 8! is shortcircuited and the voltage drop through the lamp 35 is increased, the green lamp-only is actually lighted. I v l 1 Many modifications of my invention may suggest themselves to those skilledln the art in view of the foregoing. The scope of the invention is, therefore, defined by the claims to 1011017.

What is claimed is:

1. In a circuit arrangement for feeding audio frequency currents of unsymmetric wave characteristics intcan amplifier and transducer systeam having an unsymmetric range of linearity, means operative in dependence upon the sense of an amplitude difference between wave peaks of opposite polarity of said "currents for reversing the phase of said currents, and means operative in dependence upon the amplitude level of said currents for fixing the times of such reversals.

2. Apparatus in accordance with claim 1 in which the first said means includes a pair or discharge tubes coupled to the source ofsaid. audio frequency currents. said tubes being adapted to rectify opposite half waves of said audio frequency currents.

3. Apparatus in accordance with claim 1 and having a pair of direct current amplifier tubes operative by rectified currents in the first said means, and a relay operative as a function of the total anode current through said amplifier tubes, which current varies in accordance with the disparity between the positive and negative peak levels of said audio frequency currents.

4. Apparatus in accordance with claim 1 in which the first said means includes two rectifier-s operating respectively-on opposite half wav an amplifier having at least two triode systems fed from said rectifiers, a relay operable by the ,output energy from said amplifier. and a phase reversing relay operable by' contacts of. the first r said relay.

5. Apparatus in accordance with clainr l in which the second said means-includes a aisnaldetector and a relay normally energiaable in response to the occurrence ofa moment of substantially negligible amplitude of quency currents.

occurrence of dissymmetry and an immediately subsequentoccurrence of low amplitude level of 1 said audio frequency currents, for reversing the same. 4 I. Audio wave phase reversing apparatus comprising a pair of electron discharge tubes each having an anode and a cathode, means for feeding a positive half-cycle peak of said audio wave to the anode of one tube and an immediately subsequent half-cycle peak of said audio wave to the anode of the other tube, anamplifier comprising discharge tubes having means for impressing unequal biasingcontrol potentials thereon, said amplifier being responsive to rectified currents from the first saidpair of discharge tubes in accordance with the disparity between thgpositive and negative peaks of said audio wave, a first relay thethird said audio 'fre-.

s. Apparatus'in accordance Withclaim 1. and, having means operable in dependence upon the operable in response to variations in the total anode current of said amplifier tubes, a second relay responsive to variations in the overall amplitude of said audio wave, a third relay of the polarity reversing type having a control circuit through contacts of the first and second relays, and means including said'control circuit whereby relay is caused to energize only when both first and second relays are energized, and is caused to be de-energized only when the first relay de-energizes and the second relay is simultaneously in an energized state.

8. In a voice frequency circuit arrangement,

apparatus for adapting the phase of a biased audio wave to the requirements for obtaining an optimum condition of linear amplification, said apparatus comprising an energy rectifying unit having two electron discharge tubes. means for feeding half-cycle energy peaks of one phase through one of said discharge tubes, means for feeding half-cycle energy peaks of opposite phase through the other of said discharge tubes, a pair of electron discharge amplifier tubes each under control of one of said rectifier tubesrespectively, means including unequally biased control grids in said amplifier tubes for effecting non-linear amplification of energy from said rectifying unit. a first relay operable by currents from said amplifier tubes, a second relay operable under control of the amplitude level of currents in said voice frequency circuit, a'third relay having phase reversing contacts in said voice frequency circuit. and means for causing the third relay to be operated and to be released under ioint control of the first and second relays and only when a moment of silence follows immediately upon a phase reversal of the bias in said audio wave.

reversible connections between said source,and'

said amplifier, and means operative in response to the reduction of said current to a relatively low amplitude for rendering effective the first said means, said relay being operable when the operation of the second said means immediately follows thatofthefirstsaidmeans.

10. The method of reversibly switching the connections of an audio frequency current source to a given amplifier and transducer system'having an unsymmetric range of linearity. which comprises deriving separate components of rectified energy from the half-waves of each polarity of said current, obtaining therefrom a differential component the sense of which changes with circumstances, storing said differential component until such time as the audio frequency current is momentarily reduced to an extremely low amplitude level, and then applying said differential component to eflect a reversal of said connections.

' JARRE'I'I L. HA'I'HAWAY. 

